Removable closure and method

ABSTRACT

A removable closure for blocking an opening able to resist high forces is formed by a plug assembly installed in a receptacle located over the opening, the receptacle including a smaller bore at the beginning of the receptacle and a larger bore adjacent thereto, these bores together forming an inwardly extending rim and an adjacent groove, with opposite radial clearance openings extending axially through the rim. The plug assembly includes two oblong plates mounted on a plug member, a first oblong plate threaded onto an intermediate threaded section of the plug member, a second oblong plate fixed to the end of the plug next to the first oblong plate in a crosswise orientation. The plug member is rotated to align the two oblong plates in preparation for insertion into the receptacle, and the ends thereof are then inserted into the clearance openings to position the second oblong plate entirely within the groove while leaving the first oblong plate ends interfit within the clearance openings. The plug member is rotated back to retighten the threaded engagement with the first oblong plate and to orient the second oblong plate within the groove crosswise to the first oblong plate and located behind one side of the rim to be able resist high forces exerted thereon without loading the threaded connection.

BACKGROUND OF THE INVENTION

This invention concerns removable closures for use in closing anentrance into a chamber or other opening.

In certain forming press installations, very high spring forces areneeded to return cam slides used to perform an operation on a part beingformed. The high force levels required to return the cam slide have ledto the development of “nitrogen springs”, which are sealed cylinderscontaining pressurized nitrogen gas, which is compressed by a pistonconnected to a rod, in turn driven by movement of the cam slide. Thenitrogen spring is received in a chamber in the cam slide.

While capable of generating high forces, nitrogen springs do requiresome occasional maintenance and replacement more often than mechanicalsprings.

Thus, chambers used to hold nitrogen springs have been closed bythreaded plugs so as to allow convenient access to the nitrogen springfor maintenance or replacement of the nitrogen springs.

The plug is engaged by the nitrogen spring cylinder component such thatthe plug threads are loaded by the high forces generated during machineoperation. Such presses are cycled over many thousands of cycles so thatloosening of the threaded connection may result.

It is the object of the present invention to provide a readily removableclosure capable of resisting very large forces repeated over largenumbers of cycles without loosening.

SUMMARY OF THE INVENTION

The above recited object as well as other objects which will becomeapparent upon a reading of the specification and claims are achieved bya closure comprised of a plug assembly including a plug member havingwrenching surfaces such as a hex shape formed on one end, the plugassembly also including a pair of oblong plates mounted on the other endof the plug member. The other end of the plug member has an intermediatethreaded section adjacent thereto. A first one of the oblong plates hasa threaded mounting hole and is threaded onto the threaded section ofthe plug member into tight abutment with a shoulder formed thereon, alocking washer also preferably installed abutting the shoulder.

The second oblong plate is fixed to the plug member other end, and isassembled so as to extend crosswise to the first oblong plate and iswelded to the plug member end in that orientation.

The plug assembly is designed to mate with a specially shaped receptacleat the entrance of the chamber nitrogen spring receiving chamber. Thereceptacle comprises a stepped diameter opening including a smallerdiameter outer bore and an adjacent larger diameter bore, togetherdefining a rim and an adjacent groove. A pair of opposing slot openingsare machined through the rim, sized to receive the ends of the oblongplates allowing the second oblong plate to pass into the groove which isconfigured to allow the second oblong plate to be rotated therein.

To install the plug assembly in the receptacle, the plug member isturned counterclockwise as with a wrench to rotate the second oblongplate into alignment with the first oblong plate. The plug assembly isthen aligned with the receptacle slots and fully advanced therein,causing the second oblong plate to move completely into the groove whilethe first oblong plate remains within the rim openings to be preventedfrom rotating. The wrenching end of the plug member is rotated back torotate the second oblong plate out of alignment with the slot openingsand the first oblong plate, this also retightening the threads.

The nitrogen spring directly bears on the second oblong plate whichtransmits the thrust directly into the inside wall of the rim ratherthan loading the threaded connection between the plug member and thefirst oblong plate so that cycling of the load does not produce anytendency to loosen the threads.

The first oblong plate, disposed in the slot openings and frictionallylocked to the second oblong plate prevents rotation of the second oblongplate to keep it from rotating into alignment with the slot openings andmaintaining it abutting the rim. Thus, the closure may be readilyremoved from the receptacle by rotating the plug member to loosen thethreads and bring the second oblong plate back into alignment with theslot openings, which allows the plug assembly to be pulled from thereceptacle.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a pictorial fragmentary view of a cam slide partially brokenaway showing a receptacle formed therein into which the plug assemblyshown displaced therefrom, is to be inserted.

FIG. 2 is an exploded view of the plug assembly shown in FIG. 1.

FIG. 3 is a pictorial view of a plug assembly in its initially assembledand locking condition.

FIG. 4 is a fragmentary pictorial view of a cam slide with the plugassembly inserted into the receptacle. FIG. 5 is a partially sectionalfragmentary view of a housing for a nitrogen spring with a plug assemblyinserted and locked therein.

FIG. 5A is a partially sectional fragmentary view of the installed plugassembly, the nitrogen spring partially shown in phantom lines inposition against one of the oblong plates included in the plug assembly.

FIG. 6 is a sectional view of a receptacle for mating with the plugassembly.

FIG. 6A is an end view of the receptacle shown in FIG. 6.

DETAILED DESCRIPTION

In the following detailed description, certain specific terminology willbe employed for the sake of clarity and a particular embodimentdescribed in accordance with the requirements of 35 USC 112, but it isto be understood that the same is not intended to be limiting and shouldnot be so construed inasmuch as the invention is capable of taking manyforms and variations within the scope of the appended claims.

Referring to the drawings, FIG. 1 shows a cam slide 10 in a forming dieof a type well known in the art, which has a chamber 12 for receiving ahigh force nitrogen spring (not shown in FIG. 1). The cam slide 10 isdriven laterally by the action of a cam surface when a press lowers thecam slide into a mating driver (not shown) in the well known manner. Thespring is used to return the cam slide as the press retracts the camslide 10.

The entrance to the chamber 12 is configured as a receptacle 14 toreceive and mate with a plug assembly 16 to form the closure accordingto the present invention.

The plug assembly 16 includes a plug member 18 formed with a hex shape20 at one end to provide wrenching surfaces.

The opposite end of the plug member is formed as a smooth cylindricalpin 22 sized to be slidably received through a threaded bore 24 in afirst oblong plate 26 and pressed into a centrally located bore 28 in asecond oblong plate 30 (FIG. 2).

The plug member 18 is further formed with an intermediate externalthread section 32 mating with the internal threads in a centrallylocated bore 24 in the first oblong plate 26.

A diameter 34 of the plug 18 has a locking washer 26 receiving thereoverand abutting an adjacent 30 shoulder 35.

The components of the plug assembly 16 are assembled together by firstplacing the lock washer 36 onto the diameter 34 and against the shoulder35, and then threading the section 32 into the threaded bore 24 in thefirst oblong plate 26 until firmly tightened against the washer 32 as byusing the wrenching surfaces comprised of the hex shaped end 20.

The second oblong plate 30 is assembled onto the pin end 24 in thecrosswise orientation with respect to the first oblong plate 26 as shownin FIGS. 2 and 3, and plug welded thereto to fix the same in thatorientation.

To prepare for installation, the first oblong plate 26 is held while theplug member 18 is rotated counterclockwise a quarter turn so that thesecond oblong plate 30 is parallel and aligned with the first oblongplate 26 as seen in FIG. 1. This loosens the threaded connection withthe first oblong plate 26.

The receptacle 14 comprises an outside smaller diameter boresubstantially smaller than the length of the second oblong plate 30 anda larger diameter bore 40 axially adjacent thereto, slightly larger thanthe length of the second oblong plate 30, together forming an inwardlyextending rim 38 at the entrance of the receptacle 14, defined on itsinside by one side of a groove 48.

The rim 38 is formed with a pair of opposing slot openings 42 extendingaxially through the rim 38 and which extend radially outward a distanceequal to the diameter of the groove 40.

The first oblong plate 26 and the second oblong plate 30 are of a lengthand width to just pass cross ways through the bore within the rim 30when aligned with the slot openings 42 which the ends of the plates 26,30 are fit. The second oblong plate 30 is of a similar length and isrotatable in the groove 40, the rounded ends thereof generallyconforming to the curvature of groove 40 to facilitate rotation in thegroove 40.

The slot openings 42 are configured to allow the ends of the secondoblong plate 30 when aligned with the first oblong plate 26 to beinserted into the receptacle 14 to pass through the rim 38 and into thegroove 40 which is deep enough to just accommodate the thickness of thesecond oblong plate 30 as seen in FIG. 5, with a slight axial clearanceas shown to insure that it may be rotated in the groove 40.

The groove 40 is sufficient such that the first oblong plate 26protrudes very slightly into the groove 40, to insure that the secondoblong plate 30 completely enters groove 40.

The ends of the second oblong plate 30 are rounded to match the diameterof the slot 40 to allow rotation of the second oblong plate 26 withinthe groove 40.

The leading sides 44 of each end of the second oblong plate 30 isrelieved to insure that the second oblong plate 30 may be easily rotatedin the groove 40.

The hex end 20 of the plug member 18 is rotated a quarter turn, rotatingthe second oblong plate 30 out of alignment with the slot openings 42and to be oriented crosswise to the first oblong plate 26.

This same rotation cause threads on the plug member 18 to again be fullytightened against the first oblong plate 42, this tightening creating africtional lock preventing rotation of the first oblong plate 26 on theplug member 18. This lock in turn prevents the second oblong plate 30from rotating back into alignment with the openings 42, since the plugmember 18 cannot rotate because the first oblong plate 26 is preventedfrom rotating by its being fit into the slot openings 42. Thus, movementof the plug assembly 16 out of the receptacle 14 is prevented until theplug 18 member is loosened as with a wrench.

The threaded section 32 is not loaded when a nitrogen spring 46 abutsthe second oblong plate 30, as this drives the second oblong plate 30against one side of the groove 40 as seen in FIG. 5A, so that the rim 38absorbs the axial load. Thus, cycling of the load does not impose anyforces on the threads connecting the first oblong plate 26 and plugmember 18, and this eliminates any tendency to loosen the connection. Atthe same time, the plug member 18 can be readily loosened when desiredas with a wrench to rotate the second oblong plate 30 back intoalignment with the slot openings 42 and allow removal of the plugassembly 16 and access to the nitrogen spring 46 for maintenance orreplacement.

1. A removable closure for blocking an opening into a chamber capable ofresisting high forces exerted thereon, comprising: a plug assemblyincluding an elongated plug member having a threaded intermediatesection engaging a threaded bore centrally located in a first oblongplate included in said plug assembly, a second oblong plate alsoincluded in said plug assembly affixed to an end of said plug member; areceptacle located at the entrance to a chamber to be closed, saidreceptacle including a bore of a diameter smaller than the length ofsaid oblong plates at the entrance of said receptacle, and an adjacentinner bore of a larger diameter able to receive said second oblongplate, said bores together forming an inwardly extending rim adjacentthe entrance to said receptacle and a groove adjacent said rim; saidsecond oblong plate configured to be rotatable in said groove; a pair ofopposite clearance spaces formed extending through said rim and intosaid groove, allowing said oblong plates to pass crosswise through saidspaces and said inner bore within said rim when aligned therewith, saidsecond oblong plate rotated therein into a crosswise orientation withrespect to said first oblong plate which is configured to be fit to saidspaces to be held against rotation, said rotation also tightening saidthreaded engagement of said first oblong plate on said threadedintermediate section on said plug member to create a frictional lockpreventing rotation of said plug member relative said first oblongplate, thereby in turn preventing rotation of said second oblong plateinto alignment with said spaces, said second oblong plate abuttedagainst said rim to absorb said high forces.
 2. The removable closureaccording to claim 1 further including a locking washer received oversaid plug adjacent said threaded section and section seated on ashoulder adjacent said locking washer, tightened into frictional lockingengagement therewith by advance of said plug member into said threadedbore in said first oblong plate.
 3. The removable closure according toclaim 1 wherein said second oblong plate has rounded ends facilitatingrotation thereof in said groove.
 4. The removable closure according toclaim 1 wherein said clearance spaces comprise slots each extendingradially out in opposite directions from said first bore, said ends ofboth of said oblong plates able to be inserted therein.
 5. The removableclosure according to claim 1 wherein said plug member has one or morewrenching surfaces adjacent an end opposite said end affixed to saidsecond oblong plate.
 6. A method of blocking one end of a chamber in astructure with a plug assembly so as to resist high forces applied tosaid plug assembly while enabling ready removal of said plug assemblycomprising: providing a receptacle at an entrance to said chamber formedwith a smaller diameter bore and an adjacent larger diameter bore, saidbores together form an inwardly extending rim at the beginning of saidreceptacle adjacent to a groove; forming one or more radial clearanceopenings extending through said rim; forming aid plug assembly bythreading a first oblong plate onto an intermediate threaded sectionadjacent one end of a plug member included in said plug assembly tightlyagainst an axially fixed surface adjacent thereto to create a frictionallock of said first oblong plate to said plug member; assembling a secondoblong plate onto said one end of said plug member and fixing the samethereto in a crossing orientation with respect to said first oblongplate, both of said oblong plates being configured to pass crosswisethrough smaller diameter bore when aligned with said spaces, said secondoblong plate rotatable in said groove; counterrotating said plug memberand attached second oblong plate to align said oblong plates with eachother and loosen said threaded engagement of said first oblong platewith said plug member; inserting said aligned oblong plates into saidclearance openings to position said second oblong plate entirely withinsaid groove with ends of said first oblong plate disposed within saidclearance openings, interfitting the same therein so as to preventrotation thereof; rotating said plug member to again position saidsecond oblong plate crosswise to said first oblong plate and toretighten said threaded engagement, whereby said second oblong plate ispositioned against one side of said rim to resist said high forcesexerted thereagainst, and is prevented from rotating into alignment withsaid clearance opening by interfitting of the ends of said first oblongplate within said clearance openings and by said frictional locking ofsaid first oblong plate to said plug member.